Means for avoiding the deleterious effect of detonation in internal combustion engines



June 4, 1935. o. c. BREWSTER 2,003,822 MEANS FOR AVOIDING THEDELETERIOUS EFFECT OF DETONATION IN INTERNAL COMBUSTION ENGINES FiledSept. 21, 1931 A TTORNE Y.

present in the different fuels.

Patented June 4, 1935 UNITED STATES MEANS FOR" AVOIDING THE DELETERIOUSEFFECT OF DETONATION IN INTERNAL COMBUSTIQN ENGINES -Osw'ald C,Brewster, Kansas City, Mo., assignor to Brewster DevelopmentCorporation, New York, N. Y., a corporation of Delaware Application Sepember-:21, 1931, Serial No. 563,972 3 Claims. (Cl. 123-191) My inventionrelates to a means and method foravoiding the deleterious effect ofdetonation of fuel in internal combustion engines. This detonation iscommonly known-as knocking.

It has been found by a photographic study of the flame travel in, thecombustion .space .of an internal combustion engine using gasoline as afuel, that the flame travels progressively from the ignition point atthesparkplug ata substantially uniform rate. The speed .of flamepropagation isvgenerally in-the neighborhood of '70 feet per second. Asthe .flame advances through the unburned portion of the fuel, the.products 0f combustion produce a pressure which increases rapidly. Thisincreased pressure is .formedmore or less rapidly-dependinguponthecharacteristics of the fuel. The pressure increases .until a ,pointwhere the remaining -charge .of unburned .gas which is situatedinazoneifarthest.fromthe point of ignition will burst into flamesimultaneously throughout its-entire volume. .Thislis analogous to anexplosion ordetonation. The products .Q combustion released .by thissudden burning .0 detonation of fuel ,producea'highpressure whichmanifests .itselfin what is'known as knocking The .cause of this,phenomenon is 'that'the in- :creased pressure produces .a hightemperature and this, aided bythe radiation of heatfrom'the burning fuelraises the entire mass of theunburned fuel -beyond its'kin'dlingtemperature, re

condition is reached, no "detonation-will result.

The point of detonation for a given-cylinder-and a given compressionratio will vary according-to the different chemical characteristics ofthe different fuels inasmuch as varying minimumtemperatures at whichself ignition occurwill be Gasoline containing a-deterring agent, suchas'tetraethyl'lead, iron carbonyl, or other 'so-called knock inhibitors,acts to slow down the rate of-combustion and it is believed raises theeffective temperature at which detonation occurs. Benzol, gasolineproduced fromcertainselected crude oils, and 1 gasolines produced 1bycracking un'der certain favorable conditions,-have a naturally highereffective detonation temperature so that these fuels are said to"have"anti knocking qualities.

"The ordinary gasoline from parafiin base-crudes, 0n the other hand,form a large-percentage of our 'gasoline production. This gasoline,having -a lower effective detonation point, has a tendency to knock,especially where the motor is running under heavy load conditions prwith a high compression ratio. Inasmuch as the efiicienqypf a gasolineengine increases with the initialcornpression ratio, it has been thepractice to design internal combustion engines with high compressionheads with the result that ordinary fuels will produce a severeknocking. When running at high speeds, the .lower,-manifold pressure:will result in a lower compression ,ratio.. It is ,for this reason thatknocking is usually absent at higher speeds, though. with the same fueland the same cylinder head .it will be present ,at lowerspeeds.

This condition led to the proposal of providing means to automaticallylower the compression ratio at .low s eeds. One example of a means ,foraccomplishingthisobject is shown by Kondo ,in United States Letters,Patent 1,719,705, It is observed that ,this patent provides 7 anexpansion chamber .connected to the cylinder head .,by -a mallorificeisothat at l w e dsth hi hleompression will be relieved through the orificeand int h expan ien-. amber, while-a h ehsn e'ds there will not besufficient time for the compres- .sion to escape intothe expansionchamber.

Another method has been proposed by Bullington in United States LettersPatent 1,732,395. Bullington suggests the formationof thereinp ss n sp cor t c lin e head n wh ch? pluralityof separated,interconnecting,pocketsare formed nd th com sed f i d recte into theseseparated pockets. {The spark 4 plug .located ,at a point intermediatethese separated pockets and connectedtherewithby aplurality. of ducts.'Uponsparking, ignition is supposed to. take place in the variouspockets simultaneously and this difiusion of thecompressionwave issupposed toprevent detonation.

One object ofmy invention .isto' permitthe use of ordinary gasoline in ahigh compressioniengine withoutthe occurrence. of destructive .knocking.

.A further object of my invention. is to provide;

means for wire-drawing thehigh pressure-produced by the detonatedfuel.so that-it mayibe used to perform, work smoothly, thus avoiding, thedeleterious effect ofv the knock.

The figure showsa section ;,of a cylinder head Another objectofmyinvention is to, provide equipped with one mode of carrying out myinvention. 4

In general, my invention consists in not trying to avoid the knock as isdone by Kondo or Bullington, but rather to provide means in which thedetonation may take place harmlessly and subsequently allowing thepressure generated by the detonated fuel to perform its work in a smoothand rythmical manner.

More particularly, referring now to the drawing, the cylinder l and thepiston 2 are of conventional design. The cylinder head 3 is secured tothe cylinder in the usual manner to form the combustion space 4. Asparkplug 8 is located as is common practice over thefuel valve 5. At apoint remote from the ignition point, as for example at the oppositeside of the combustion,

space, a gasoline combustion chamber 6 is joined to the main combustionspace 4 by an'opening I which is moreor less restricted, depending uponthe compression ratio and the distance it is located from the ignitionpoint. The size of the chamber 6 will vary, depending upon thecompression ratio desired. For a high compression ratio, the chamber 6may be of a constant size and a smaller clearance provided between thetop of the piston 4 and the cylinder head. The chamberfi may be variedwithin certain limits to vary the compression ratio. It must, however,be of a sufficient size to perform its function. This function will behereinafter more fully described. The total volume of the combustionspace 4 and the chamber 6 is used as the clearance volume in computingthe compression ratio of the engine.

When the piston 2 is forced upwardly, it compresses the fuel and airmixture into the combustion space and the chamber 8, it being understoodthat the opening 1 leading to the chamber 6 is of sufiicient size sothat during the compression stroke the pressure in chamber 5 issubstantially the same or. only slightly less than that in the maincombustion space, 4, that is that the pressure drop of the gas mixturein being forced through opening I is small. The ignition system is timedas in the ordinary engine, to produce a spark at the spark plug 8 atsome predetermined point of the compression stroke, usually from 15 to30 of the angular crank travel head of the top dead center. The flamestarts to travel progressively through the fuel mixture in alldirections away from the spark plug in concentric, increasingly largercircles. There is usually an interval of slow travel at the start due tothe comparatively lower pressure. The speed of flame travel increases asthe pressure. As the pressure increases, the speed of travel increases.The highest speed is usually reached by the time the piston hasarrived'at the top of its stroke. The heat generated by the combustion,as well as the fact that the products of combustion occupy a greatervolume than the original mixture, results in a rapid rise in thepressure existing in the combustion space. This results in the flow ofgases into the chamber 6 again with a relatively small pressure drop. Itnow becomes apparent why I have placed the chamber 6 as far as possiblefrom the spark plug. It is obvious that the gases in chamber 6 willconsist chiefly of the unburned fuel mixture. The pressure andtemperature having been increased due to partial combustion of themixture, will produce the temperature of self ignition. The detonationalways results from the explosive burning of the remainder of unburnedmixture. This unburned mixture has been substantially isolated inchamber 5. If detonation rod and the valves.

. cure. When, however, due to the increase of pressure and temperature,the self ignition point or detonation point isreached, it will occur ashas been seen, in chamber 6.

'I'hisdetonation results in a very high pressure occurring almostinstantaneously. Due to the restricted opening I, this high pressure isnot transmitted to the working chamber 4 and is thus deprived of itsdestructive efiect upon the piston, the wrist pin, the crank bearings,the connecting The noisy effect which is noticed and from which knockingderives its name, is obviated. It is to be noted that the duct 1 is sodesigned that, while it is'large enough to produce only a small pressuredrop at the compression pressure, yet it will'be small enough to producea substantially wire-drawn effect for the high pressure produced bydetonation; The pressure of detonation being wire-drawn through opening1 allows this pressure to enter the working chamber 4 and to contributeits effect on the piston to do work. Thus it is seen that, during thecompression period and the earlycombustion stage, the velocity of thegases flowing through opening 1 and into chamber 6 is relatively low sothat a low pressure drop takes place.

On the other hand, when the detonation occurs, the velocity is increasedin the opposite direction, thus giving the very high pressure drop withits resulting wire-drawing effect during this stage. The pressure drop,of course, varies with the velocity.

It is to be understood that, while I have shown one mode of carrying outmy method, that various changes may be made in the details within thescope of the claims appearing below without departing from the spirit ofmy invention. It is, therefore, to be understood that my invention isnot to be limited to the specific details shown and described.

Having thus described my invention, what I claim is: a

1. In an internal combustion engine, a cylinder head adapted to form acompression space with the piston, ignition means located in saidcompression space, a chamber communicating with said compression spacethrough an orifice of reduced diameter, adapted to receive a portion ofthe fuel, said chamber being positioned at a point substantially mostremote from the ignition means whereby the fuel contained therein willbe ignited subsequent to the burning of the fuel in said compressionspace, whereby detonation will be substantially segregated in saidchamber, and the shock of detonation on said piston will be reduced bysaid orifice.

2. In a device of the kind described, a main combustion chamber havingan ignition point in which the combustion of gases takes place byrelatively slow flame propagation, an auxiliary chamber in which thecombustion of gases takes place by detonation due to increased pressure,said auxiliary chamber having an aperture in the path of travel of flamepropagation in the main combustion chamber and of a sufficientlyrestricted area to permit the escape of gases from the auxiliary chamberaccompanied by a reduction of pressure, said aperture being positionedat a point substantially most remote from the ignition point.

3. In a device of the kind described, a main 5 combustion chamber, anauxiliary chamber having an opening into the main chamber in the path oftravel of the flame front and restricted in area to the extent ofpermitting differences in pressure between the main chamber and theauxiliary chamber, said opening being positioned at a pointsubstantially most remote from the ignition point.

OSWALD C. BREWSTER.

